Production and corrosion behaviour of micro-arc coated magnesium alloys

The current study is composed of two stages. In the first stage, in order to investigate theeffect of alloying elements and treatment time, the thickness of 10 micrometer (K10) and25 micrometer (K25) ceramic coatings were fabricated on different chemical compositionhaving AZ91D, AZ31B, AM60B and AM50B magnesium alloys in alkaline phosphatebased electrolyte by micro-arc oxidation method using with a pulsed bipolar direct current(DC) power supply. In the second stage, the effect of different sealant post-treatments oncorrosion resistance of micro-arc oxidation (MAO) coated AM60B and AM50Bmagnesium alloys were investigated.The surface morphology and elemental composition of produced MAO coatings wasdetermined using Scanning Electron Microscope (SEM) equipped with Energy DispersiveX-ray Spectrometer (EDS). The crystallographic phase analysis and identification of MAOcoatings was carried out by X-ray diffraction (XRD). High resolution surface profilometerwas used for mapping of the 3-Dimensional surface features and roughness.Electrochemical tests conducted using potentiodynamic polarization technique in 3.5percent NaCl solution at room temperature in order to evaluate the efficiency of sealed andunsealed MAO coatings on the corrosion resistance of magnesium alloys.The results displayed that enhanced corrosion protectiveness was provided by MAOcoatings formed on different magnesium alloys. It is observed that the microstructure andchemical composition of magnesium alloys is crucially effective on the formation,structural and corrosion properties of MAO coatings. Further corrosion protection isachieved by applying alkaline post treatment processes.